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Shutemov" , Zi Yan , Baolin Wang , linux-mm@kvack.org, linux-kernel@vger.kernel.org, opensource.kernel@vivo.com Subject: Re: [PATCH] mm: Skip the reserved bootmem for compaction Message-ID: <5fmd2poyeas2pomho2io5zgmqd26vnxd77czmlhqn5tapy4fv4@5tdcqamzgyj5> References: <20240902122445.11805-1-rongqianfeng@vivo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20240902122445.11805-1-rongqianfeng@vivo.com> X-F-Verdict: SPFVALID X-Titan-Src-Out: 1725448437903432177.12802.4636682366867047228@prod-euc1-smtp-out1001. 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This kind of memory can't be > used as migration sources and targets, skip it can bring some performance > benefits. > > Because some drivers may also use PG_reserved, we just set PB_migrate_skip > for those clustered reserved bootmem during memory initialization. > > Signed-off-by: Rong Qianfeng I'm not convinced the savings due to skipping a few pages during the scan would justify the additional code. There would have to be a large number of reserved pages scattered throughout the zone to make a difference and even that situation would be a big surprise. I'm not even sure this can be explicitly tested unless you artifically create reserved pages throughout the zone, which would not be convincing, or know if a driver that exhibits such behaviour in which case my first question is -- what is that driver doing?!? -- Mel Gorman SUSE Labs